<div class="container">
  <app-new-problem></app-new-problem>
  <div class="list-group">
    <a class="list-group-item" *ngFor="let problem of problems"
     [routerLink]="['/problem', problem.id]">
      <span class="{{'pull-left label difficulty diff-' + problem.difficulty.toLocaleLowerCase()}}">
        {{problem.difficulty}}
      </span>
      <strong class="title">{{problem.id}}. {{problem.name}}</strong>
    </a>
  </div>
</div>